Re: question about HDF5 parallel use of unlimited dimensions...

On Thu, 30 Jun 2005, Ed Hartnett wrote:

> As I understand it, using fixed-length data, my different processes
> could write their data and go on their merry way, without waiting for
> anything.

This can be done only if you know that the different processors are
not updating the same chunk.

Fixed vs extended is not relevant to the basic issue: you must
coordinate all writes in parallel.
> 
> As currently implemented, H5Dextend is called when needed as you write
> the data in netcdf. That is, if you are writing a record at a time,
> H5Dextend is called for each record.

This will be quite slow in parallel. But it will work.

Presumably, user's can control this by batching the writes.

-- 
Robert E. McGrath
National Center for Supercomputing Applications
University of Illinois, Urbana-Champaign
Champaign, Illinois 61820
(217)-333-6549

mcgrath@xxxxxxxxxxxxx